Device for detecting transmission losses by means of measurements

ABSTRACT

In a device for detecting transmission losses of optical light guide means ( 2 ) of an endoscope ( 3 ) by means of measurements, said optical light guide means ( 2 ) having an optical inlet portion ( 4 ) through which light from a light source ( 6 ) is transmitted to an optical outlet portion ( 8 ) of the means to be checked, said device comprising at least one light sensor ( 10 ) measuring the light intensity emerging from the optical outlet portion ( 8 ) of the means ( 2 ) to be checked, and an evaluation means ( 14 ) for the signal of the at least one light sensor ( 10 ), said evaluation means ( 14 ) having a display means ( 18 ) for displaying the measurement result, it is provided that the at least one light sensor ( 10 ) is arranged in a chamber ( 20 ), that the optical outlet portion ( 8 ) of the light guide means ( 2 ) to be checked is adapted to be introduced through an opening ( 22 ) of the chamber ( 20 ) into the chamber ( 20 ), and that the inner surface ( 24 ) defining the chamber ( 20 ) diffusely reflects the light emerging from the optical outlet portion ( 8 ).

BACKGROUND OF THE INVENTION

The invention relates to a device for detecting transmission losses ofoptical light guide means of an endoscope by means of measurements.

An examination of endoscopes and associated light guide cables hasfrequently shown that the light guide means suffer high transmissionlosses. Due to mechanical stress, such as bending and winding-up of thelight guide cable, tensile stresses when a light guide cable is stronglypulled, bending of the endoscope shaft, and thermal stress duringhot-steam sterilization, individual fibers of the light guide means maybreak. Frequently, there are deposits on the optical inlet and outletsurfaces of the optical inlet and outlet portions. These deficiencies donormally not lead to an immediate failure of the overall illuminationmeans but to a progressive deterioration of the transmission. Owing tothe gradual transition to higher transmission losses the deteriorationof the illumination intensity is frequently detected too late. If thesurgeon notes during an operation that the endoscope used cannotadequately illuminate the operating area, he has to stop the operationin most cases since there is no further sterilized endoscope availableto him.

It would therefore be necessary to check the endoscopic instrumentsprior to their use.

Instruments for determining various photometric measured variables areknown. These instruments use an optical sensor for detecting the lightemerging from the light source via the light guide means.

DE 35 15 612 A discloses a light source instrument for an endoscope witha checking means for the light source. An examination the light guidecables or an endoscope is not intended.

In DE 43 25 671 A a method and a device for measuring the damping effectin light wave guides using a pulsed light transmitter is disclosed. Thetransmitter signal is subjected to a pulse frequency modulation with theaid of which variations in the output power are eliminated. Thismeasuring method is very exact but too complex for quickly checkinglight guide means in operating theaters.

From EP 0 416 408 A a checking means is known where the light source ofthe endoscopic means comprises a beam splitter in the beam path. Aportion of the light beam is directed to a first sensor, while the otherportion is directed via a light guide cable to be checked to a secondsensor. By comparing the measured values of the first and the secondsensor the transmittance is determined. It is of disadvantage that twolight sensors are required which may have different sensitivities andthus have to be calibrated. Splitting of the light beam with the aid ofa beam splitter also requires careful calibration. The checking meansdoes not possess its own light source and therefore depends on the lightsource of the endoscopic means such that additional brightness limitvalues must be fixed to assess the light intensity of the light source.It is disadvantageous that the checking means is integrated into anexisting endoscopic equipment and cannot be generally used for checkinglight guide means of an endoscope. In particular, the known means allowsonly light guide cables or the lamp of the light source of a specificmeans to be checked, but not the endoscope proper.

SUMMARY OF THE INVENTION

It is therefore an object of the invention to provide a device fordetecting transmission losses of optical light guide means of anendoscope by measurements, said device allowing rapid checking ofdifferent light guide means independent of the light source of theendoscopic means.

This object is achieved with the features of claim 1.

The invention advantageously provides that the least one light sensor isarranged in a chamber, that the optical outlet portion of the lightguide means to be checked is adapted to be introduced through an openingin the chamber into the chamber, and that the inner surface defining thechamber diffusely reflects the light emerging from the optical outletportion of the means to be checked.

The arrangement of the light sensor in a diffusely reflecting chamberoffers the advantage that the light emerging from the means to bechecked can be detected to a large extent independent of its directionand its input cross-section. It is therefore possible to check differentlight guide means of different manufacturers for their transmissionlosses. Even the light guide means of endoscopes can be checked withoutlarge expenditure and with a high degree of reproducibility of themeasured values. The entry of extraneous light at the opening of thechamber is reliably prevented, e.g. with the aid of one or a pluralityof flexible seals. The device according to the invention is universallyusable, independent of the endoscopic means, and is suitable for quicklyexamining light guide means prior to an operation. In particular, it isno longer necessary to return an endoscope to the manufacturer for thepurpose of examining its transmission losses.

Preferably, it is provided that a separate light source, which isindependent of the means to be checked, couples a predetermined lightintensity into the optical inlet portion of the light guide means to bechecked. The employment of a separate light source offers the advantagethat a defined predetermined light intensity can be used for checkingpurposes without a recalibration of reference values having to beperformed for each check. Endoscopic means normally use halogen lamps orgas-discharge lamps. These light sources possess a high radiation powerand are mostly controlled such that the adjustment of a reproducible andconstant light intensity is difficult. Further, these light sources aresubject to an ageing process such that fixed control values also need tobe recalibrated. In contrast to this, a constant light intensity can beassumed when an independent checking light source is used which must notbe permanently calibrated.

Particulary advantageous is the use of a light-emitting diode as a lightsource. Since the measurement of the transmission losses does notrequire high light intensities, it is possible to employ alight-emitting diode. Said diode is inexpensive and can be adjusted byconstant-current control to an adequate and highly reproducible lightintensity. Calbration is thus not necessary since a fixed and storedreference value can be used for the light source which is solelyemployed for checking purposes.

According to preferred aspect of the invention the light source isarranged in a connector adapted to standardized connections of theoptical inlet portion of the means to be checked. The connector adaptedto the standardized connections allows the light source to be quicklyconnected to the inlet side of the light-conducting means and reliableseating on the means to be checked.

According to a preferred aspect the inner surface of the chamber is ofspherical configuration. It is of importance for the measurig accuracythat the entire transmitted light is detected and evaluated. Endoscopesilluminate e.g. the place of observation at differently large apertureangles depending on the embodiment and the application. Further, thelight can emerge from the light guide means at an angle relative to theinstrument axis. The chamber defined by a spherical inner surface iscapable of diffusely reflecting the entire light emerging from theoptical outlet portion independent of the radiation angle and thediameter of the light exit such that the at least one light sensorarranged in the chamber can measure the entire light with a high degreeof reproducibility. For this purpose the inner surface of the hollowsphere is provided with a diffusely and highly reflecting white coatingor is made from a material with corresponding properties. The light issubjected to multiple reflection by this coating whereby theillumination intensity in the chamber containing the light sensor ishomogenized.

In front of the light sensor a diffusion disk may be arranged whichprevents light emerging directly from the light outlet portion of thelight guide means to be checked from impinging directly onto the lightsensor. The spherical chamber thus ensures insensitivity of themeasurement with regard to the direction of the light emerging at theoptical outlet portion of the light guide means to be checked and withregard to the exact position of the optical outlet portion inside thechamber.

A photodiode is used as light sensor.

In the evaluation means a reference value for the light intensity of thelight source can be stored, wherein the evaluation means proportions, asa measure of the transmission losses, the light intensity measured bythe light sensor to the reference value, and displays e.g. a percentagevalue.

The reference value for the light source can also be read into theevaluation means by directly connecting the light source to the openingof the chamber and measuring the reference intensity.

Such an approach is useful e.g. when the light source is replaced byanother or a new light source.

Further, reference values for transmission losses for specificendoscopic means to be checked can be stored in the evaluation meanssuch that the evaluation means can display any exceeding of givenminimum transmission values.

BRIEF DESCRIPTION OF THE DRAWING

Hereunder an embodiment of the invention is explained in detail withreference to the drawing. The only FIGURE shows the device according tothe invention for detecting transmission losses of an endoscopic meansby measurements.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The device for detecting transmission losses of optical light guidemeans 2 of an endoscope 3 by means of measurements shown in the onlyFIGURE comprises an evaluation means 14, a light source 6 which isindependent of the means 2 to be checked, and a light sensor 10 arrangedin a hollow sphere 36.

The evaluation means 14 is provided with a display means 18 fordisplaying the measurement result, as well as an electronic circuit 16which comprises on the one hand a constant-current supply unit for alight source 6 consisting of a photodiode, and on the other hand astorage means for reference values for the light source used and for thelight guide means to be checked. Further, the electronic circuit 16comprises an input for the output signal of the at least one lightsensor 10, which signal is fed via an amplifier 12 to the electroniccircuit 16. The electronic circuit 16 proportions the amplifiedmeasuring signal of the light sensor 10 to a predetermined referencevalue and displays the measurement result on the display means 18. Thetransmission loss can e.g. be displayed as a percentage value. Thus theuser obtains a measure for the transmission loss of the light guidemeans 2 to be checked. These light guide means 2 consist e.g. of lightguide cables or light guide fibers contained in the endoscope. Whenreference values for transmission losses are stored for specific lightguide means 2, it is possible to display the measured transmission lossin relation to a new or reference instrument.

The light guide 6 preferably consists of a light-emitting diode arrangedin a connector 28. The connector 28 fits e.g. on the standardizedendoscope connection 32 for light guide cables.

The connector 28 further fits on the inlet connection of the light guidecable. Thus it is possible to examine either endoscopes or light guidecables or other light-conducting light guide means, wherein an adapterpart for the connection of the light source 6 may be required.

According to the FIGURE, the distal end of the endoscope 3 is introducedthrough an opening 22 into a chamber 20 of a hollow sphere 36. Theopening is suitably sealed against ambient light e.g. by one or aplurality of rubber seals not shown in the FIGURE.

The inner surface 24 of the hollow sphere is provided with a matt whiteand highly reflecting coating or consists of a matt white highlyreflecting material, e.g. Teflon, such that the light emerging from theoptical outlet portion 8 at the distal end of the endoscope 3 isdiffusely reflected at the inner surface 24 of the hollow sphere 36.

The homogenized light reflected and diffusely scattered in the chamber20 is measured by the light sensor 10, wherein a diffusion disk 40 canbe arranged in front of a light sensor 10 consisting of a photodiode toprevent direct light from the optical outlet portion of the light guidemeans 2 from being applied to the light sensor 10. This is necessary inparticular when e.g. the illumination means of the endoscope 3 generatesa wide light cone at the optical outlet portion 8.

The light sensor 10 of the embodiment shown in the only FIGURE isarranged at an 90° angle relative to the opening 22 of the chamber 20.The opening 22 can of course be arranged at an angle of less than 90°relative to the optical axis of the light sensor 10. With the aid of thediffusely reflecting inner surface 24 of the hollow sphere 36 and thediffusion disk 40 the light sensor 10 can perform a measurement with ahigh degree of reproducibility and accuracy independent of the angle ofincidence of the light at the opening 22 and under homogenization of theincident light. With the aid of the evaluation means 14 the transmissionloss between the optical inlet portion 4 and the optical outlet portion8 can then be determined in a simple manner at a minimum expenditure oftime.

Although a preferred embodiment of the invention has been specificallyillustrated and described herein, it is to be understood that minorvariations may be made in the apparatus without departing from thespirit and scope of the invention, as defined by the appended claims.

1. A device for detecting transmission losses of optical light guidemeans comprising optical light guide means (2) having an optical inletportion (4) through which light from a separate light source (6) istransmitted to an optical outlet portion (8) of the light guide means(2), at least one light sensor (10) arranged in a chamber (20) formeasuring the light intensity emerging from the optical outlet portion(8) of the light guide means (2) to be checked and diffusely reflectedin the chamber (20), evaluation means (14) for evaluating the measuringsignal from the at least one light sensor (10), the evaluation means(14) having a display means (18) for displaying the measurement result,said optical light guide means (2) is part of an endoscope (3), saidoptical inlet portion (4) of said light guide means (2) to be checked islocated at the optical inlet portion (4) of the light guide means (2)contained in the endoscope (3), said separate light source (6) isindependent of the light guide means (2) to be checked contained in saidendoscope (3) couples a predetermined light intensity into the opticalinlet portion (4) of said endoscope (3), and the optical outlet portion(8) of said endoscope (3) is introduced through an opening (22) of thechamber (20) into the chamber (20).
 2. The device as defined in claim 1wherein the light source (6) consists of a light-emitting diode.
 3. Thedevice as defined in claim 2 wherein the light source (6) is arranged ina connector (28) which is adapted to the connection (32) of the opticalinlet portion of the light guide means (2) to be checked.
 4. The deviceas defined in claim 1 wherein the light source (6) is arranged in aconnector (28) which is adapted to the connection (32) of the opticalinlet portion of the light guide means (2) to be checked.
 5. The deviceas defined in claim 1 wherein the chamber (20) comprises a sphericalinner surface (24).
 6. The device as defined in claim 1 wherein adiffusion disk (40) is arranged in front of the light sensor (10), whichdiffusion disk (40) scatters the light from the optical outlet portion(8) of the light guide means (2) to be checked which directly impingesonto the light sensor (10).
 7. The device as defined in claim 1 whereinthe axis of the light emerging from the optical outlet portion (8) ofthe light guide means (2) to be checked through the opening (22) of thechamber (20) has an angle of ≦90° relative to the light detection axisof the light sensor (10).
 8. The device as defined in claim 1 whereinthe light sensor (10) consists of a photodiode.
 9. The device as definedin claim 1 wherein a reference value for the light intensity of thelight source (6) is stored in the evaluation means (14), and theevaluation means (14) calculates the transmission loss as the quotientof the light intensity value measured by the light sensor (10) and thereference value and displays it as a percentage value on the displaymeans (18).
 10. The device as defined in claim 9 wherein the referencevalue is adapted to be read into the evaluation means (14) by directlyconnecting the light source (6) to the opening (22) of the chamber (20)and measuring the reference light intensity.
 11. The device as definedin claim 10 wherein for predetermined endoscopic light guide means (2)to be checked, minimum transmission values are stored in the evaluationmeans (14), which minimum transmission values are adapted to be recalledas reference values during the measuring process.
 12. The device asdefined in claim 9 wherein for predetermined endoscopic light guidemeans (2) to be checked, minimum transmission values are stored in theevaluation means (14), which minimum transmission values are adapted tobe recalled as reference values during the measuring process.
 13. Thedevice as defined in claim 1 wherein the chamber (20) is arranged in ahollow sphere (36).